So I went to PetCo the other day JUST TO LOOK and ended up going back yesterday to take home a betta I fell in love with. I loved his colors and I also noticed he had some sort of weird lump towards the base of his tail and on one side. He also swam kinda sideways, but I couldn't really tell while he was in his little cup.
So I set up and transfered him into his new tank today. I floated his cup in the water for a bit and then released him slowly. Well, ever since then he has really been swimming strange.
He'll swim upside down, flail around, float to the top, lay on the bottom, stand vertically looking up, etc. He will rest for a few second before doing it again. I took a video of his behavior.
I'm worried for him :( However, during the time it took to upload that video to YouTube (because my internet is slower than a snail), he seems to have calmed down a bit and is acting "normal." He's upright and floating around, swimming occasionally. Maybe he just freaked out over his new tank?